Piston



March 8, 1938. R. R. TEETOR 2,110,345

- f PIsToN Filed July 3l, 1954 Patented Mar. 8, 1,938 i UNITED STATES PATENT OFFICE rrs'roN Ralph R. Teetor, Hagerstown, In assignor Ato The Perfect Circle Company, Hagerstown, Ind., a corporation of Indiana Application July 31, 1934, Serial No. 737,800

6 Claims. (Cl. 309-13) This inventionr relates to pistons for internal of the piston while Vthe piston is being rotated. combustion engines and the like. The skirt after the sizing operation and while the The principal object of my invention is to propiston head is hot is round or cylindrical. Upon vide a piston so constructed that the desired cooling of the piston, the head shrinks more than clearances between the skirt and cylinder Wall at the skirt and the hangers, being connected rigidly 5 right angles to the piston pin may be maintained and directly to the top of the' skirt, pull in the throughout the operating range of the engine. I portions of the skirt in line with the pin bosses so provide a piston of aluminum alloy or the like that the skirt becomes elliptical with the major which is simple in structure and cheap to manuaxis at right angles to the axis of the pin bosses.

10 facture, while at the same timefthe piston is free Using this cooledpiston as a pattern, I form a 10 from the objectionable defects present in the cam to be used in a machine which will formslotted skirt type of aluminum pistons now on the turn or grind the skirts of `other pistons in promarket. duction to the desired elliptical form.

The above and further objects of my invention With the piston in the cylinder, when the enwill appear more fully from the following degine is cold there is the correct clearance between l5 scription, reference being had to the accompanythe cylinder wall and the bearing surfaces of the in'g drawing in which: i piston skirt which are midway between the piston Fig. 1 is a vertical sectional view through `a pin bosses. As the engine becomes heated in piston embodying the preferred form of my inoperation, the piston head is heated to a much vention; higher temperature than the skirt with the result 2o Fig. 2 is a vertical sectional view through the that the head tends to expand twiceas muchas piston, the section being at 90 to that of Fig. 1; the skirt or thereabout. The expansion of the Fig. 3 is a cross sectional view through the head separates the hangers and thus increases the piston, takenon line 3-3 of Fig. 1; and n diameter of the top of the skirt in the plane of Figs. 4 and 5 are plan and side views, respecthe axis of the pin bosses, the hangers being 25 tively, of one of the cross struts. inflexible and connected directly to the upper Thepistoncomprises ahead I6 separated from portion of the skirt. In other words the expanthe skirt I1 by the slot I8. 'I'he skirt is prosion of the head tends to change the upper porvided with piston pin bosses I8 and the head, tion of the skirt from its elliptical form to one upper portion of the skirt and the bosses are conapproaching a round form by increasing the 30 nected together by integral hangers or webs 20. diameter in the plane of the pin bosses so that it 'Ihe piston is formed of the usual aluminum alloy approaches the diameter at right angles thereto. or the like. 'I'his tends to decrease the latter diameter. At Near the bottom of the skirt are two cross the same time, however, the aluminum of the struts 22, formed of metal known as Invar, or skirt expands circumferentially due to the heat, steel or some other suitable metal having a lesser so that -while the expansion of the head may coemcient of expansionthan the head and skirt. tend to reduce the major axis which is at right As illustrated in Figs. 4 and 5, one form o! each angles to the pin bosses, yet the inherent expanstrut may be L-shaped in cross section and have sion of the skirt slightly more than compensates 40 inclined end ears 23 provided with apertures 24'. for this with the result that the desired clear- 40 As best shown in Fig. 3, the end portions of the ance at the top of the skirt bearing faces is mainstruts including the apertured ears 23 are emtained. In other words, the distance between bedded in thickened portions 25 of the skirt. the bearing, faces increases slightly as the diam- In.` casting the piston, above described, the eter oi' theengine cylinder increases.

cross struts are mounted in arnold and the piston The struts 22 also perform the function of 45 is then cast so that the ends of the struts are emmaintaining this desired clearance at the bottom bodied in the thickened portions of the piston of the bearing faces. After the piston is cast the skirt. In order to impart to the skirt the desired aluminum cools so, of course, the struts are alelliptical or out of round shape or form, I prefways in compression and they tend4 to maintain erably take a piston after it has been cast, heat the diameter of the lower ends of the bearing 50 the head to approximately the temperature to faces about the same when'the piston is cold as which the head would be heated under normal when it is hot. As the skirt becomes heated duroperating conditions in an engine and then while ing operation of the engine, the aluminum exthe piston is in this heated condition size it by pands circumferentially but the expansion neca tool brought into engagement with the skirt essarily takes place for the most part on the 55 fsb Gil

minor axisof the skirt. This may tend to flatten 'out the bottom portions of the bearing faces between the ends of the struts but this tendency is slightly more than compensated for by the circumferentialexpansion ci the skirt, so'that as the diameter of the engine cylinder increases,

'the distance between the bottom portions of the bearing faces increasesand the correct clearance between the cylinder wallvand the bearing faces is maintained.

It will thus beseen thai; the diameterof the'KV piston skirt from top to bottom is'properly controlled during the operating range oi' the engine so that the desired clearance between the bearing faces and cylinderwallis maintained throughout their length, thediameter of the skirt in line with the pin bosses being permitted vto change without 4impairing the emciency of the engine. and without danger of scoring and the like.

It is understood that my invention is not limited to the details of construction shown and that other forms may be used without departing iromV the scope. of my invention.

I claim: l.1n-a piston'V formed of metal havinga high coeiiicient `of expansion, ahead.. a continuous skirt of elliptical form'in rcross-section from one end thereof to the other, the upperedge of said skirt being separated from said headby a slot extending substantiaily throughout the circumferenceof the piston. rlgid'hangers connecting l'together said head and the upper end of said "head and integrally connected to of saidskirt von the rminor axis ofthe 'ellipse of stantially spaced apart whereby of such length that they kkli'l: free and unrestrained skirt, piston 1 pin bosses on skirt and on the minoraxis o'f the ellipse of saidskirt, and a pair -of struts eachformed of a material having a' much'lower'ccemcient of expansion than Vsaid skirt and disposed within said" skirtbelo'w. Said pin bossesand parallel to the major axis of the.

ellipse of said skirt with their ends Vembedded in jthewalirof-said skirt'at points substantially spaced apart.v said vstruts and constructed that they are iniiexible and are compression by said skirt, the force of compression. being sutli'ciently great that it will not be by; thermal expansion'ot said skirt durreleased ing operation ln an engine.

2. In s piston formed ormetsi having a high' head, a continuous-- coeiiiclent 'of expansion, a walled skirtr having an elliptical cross-sectional shapefrom one endto'the otheryop'posed rigid hangers integral with and depending from said the upper end the latter, said headbeing` separated from the upper end of said skirt atall .points except at said hangers whereby said head is i'reeto expand .and contract in a uniform manner and without bosses formed on said pis-.

distortion, piston pin ton adjacent .the lower ends of sait'l' hangers 'with the'remainder of the upper wall portion of said y .whereby expansion and contractionmovements of saidhead acuate seid 'hangers to-expandzand contract said skirt along the'minor axisof its el1ipseto-.produce, uponl expansion, a substantially circular skirt and, upon contraction, an elliptical skirt, ,and a pair of struts each formed of la material having a. y

mulch lower .coeiiicien y,of expansionl than said skirt and disposed within said skirt below said pin bosses and parallel to themajor axis/of the ellipse of said'skirt with their ends integrally secured inthe wall of said skirt the skirt ma'- "terial between adjacent ends of said struts is free k2,110,345 t y to tend to satten out during thermarerpshsinnf these portions oi?v in g inflexible so that the expansion of the vform to one approaching a round form,

eachbeingsoshaped.

are held under constantl l vskirtv directly connected to at points subof the piston skirt, said struts each being so shaped and constructed that they are iniiexibie and are of such length that they are held under constant compression by said skirt, the force of i compression being suiiicientlygreat it will not bereleased by the thermal expamion of said skirt during operation in an engine.

therebetweenv extending substantially throughout the circumference of the piston, H

bosses integral with the skirt and on the minor axis of the latter, hangers integral with the head and upperportionl ot the skirt, the hangers upon beingiheated in anengine tends to the upper portion of the skirt fromI its elliptical struts having a lower coemcient of expansion than said skirt and arranged parallel to the major axis of theskirt in the lower portion of the skirt, the struts with the skirt and being of such length that they are held under constant compression by the skirt so that the circumferential expansion ofthe skirt upon becoming heated in an engine tends to change the lower portion ofthe skirt from its elliptical 'form to one'approaching a round form.

the length of the major axis remaining substantially constant. t t A 4. In a piston formed of metal having a high coemcient of expansion, `al. head. a continuous walled skirt having an` elliptical cross-sectional shape with the bearing face portions on the major axis, pistofpin bosses'on the minor. axis ofthe ellipse oi' the skirt, and two spacedhaving their ends imbedded' struts having-a lower coemeient `ofgexmimicn l than said skirt anddlsposed within 'said lkii't 4below and spaced from said-pin bosses and substantially parallel to the maior axis of said ellipse'. the struts being inflexible and the face'portions between the ends of the struts being flexible, whereby said bearing face portions tend toilatten out during thermal expansion of the pistonskirt and the V'lengthof the minor axis `of theskirtincreasessi f 5. In a plston'fonned oi'imetal having a high 4coeiilcient of expansion, a continuous walled skirt having. an elliptical cross-sectional shape from one endtto the, other with the face' portions on` the major opposed hangers rig-` idly connecting the upper end of the/skirt to the head on the Vminor axis of the ellipse of the skirt. the skirt ,being separated from the head vbetween rthe hangers, piston pin `bosses within the' skirt and on the minor axisof the kellipse of the mrt. and two spaced apart struts having 'a 'lower coeiiicient of expansion thanv said 'skirt and di posed Hwithin'said skirt'below and-spaced from said pin bosses, and substantially parallel tothe major axis of said ellipse.'v the struts being inf ilexible and the. bearing face'portions between the ends of the struts being dexible whereby said4 lbearing face portions tend Vto'tiatten out during 'rthermal expansion of ythepiston irt and the length vof the minor axis of the'skirt increases.r

6. A piston comprising "a head,-rigid hangers depending lfrom said ,head` yand carrying pin bossesaperturedtoreceiveapistonpimanda v said hangers and bosses, all formed of a metal having a high coefficient of expansion; said head and skirt being txiailyspacea from each other throughout theirl hearing entire circumference by a circumferentially extending air gap and being maintained in such relation by said rigid hangers. the entire exterior surface of said skirt being generally elliptical in contour with the minor axis thereof substantially parallel to the axis Iof said pin bosses and the continuity of said skirt being' interrupted only by the pin boss apertureaand a pair of rigid struts having a lower coemcient. of expansion than that of the metal of said skirt disposed below and spaced from said pin bosses, the ends of l said struts being embedded in the metal of said 5 skirt.

RALPH R. TEETOR. 

